This invention is in the field of safety devices for oil burning heaters to prevent overheating or loss of oil when inoperative.
Due to a predominance of cold and wet weather, many owners of both commercial and pleasure marine vessels in many regions prefer oilstoves to other types of heat. LP gas and gasoline stoves are hazardous due to their flammability and explosive nature. Alcohol stoves generate moisture. Electric heat is prohibitive unless used only while moored to a source of commercial power or if boat is equipped with high voltage power generation. All are inferior to oil heat's steady, less costly, high BTU generation and its ability to be left on for extended periods, keeping moisture and mildew in the cabin at a minimum. Thus, many owners will remove a commercially installed heater and replace it with an oil stove.
Leaving an oilstove unattended, however, has been a disaster to many boat owners. Flooded stoves have burned up many vessels and many a battery has been discharged and the oil pump burned out when the oil storage tank has run dry.
Marine stove installations are basically either gravity fed from a tank above the heater or pump fed from a tank level with or below the oil heater. There are also two basic systems for feeding oil to the burner, the drip valve type that is manually operated but which is hard to adjust since the viscosity of the oil decreases as the heater warms up and thus dangerously increases flow to the burner pot. The other type comprises a carburetor having float valves which are provided in an effort to provide a safety feature preventing flooding but such devices have no shut-off means in the event of excessively high temperatures.
Installations heretofore have included various combinations of the above metering systems. None are acceptable to be left unattended. For positive excessive high heat and/or low heat protection, a heat operated safety control to interrupt the oil supply is most desirable. The necessity for excessive high heat protection goes without comment, but protection against too low or no heat bears some explanation:
1. Wind or other draft conditions often times blow out a flame left on low, thus oil continues to flow into a hot stove pot, vaporizes and could be reignited by a "hot spot" or other source.
2. A charge of water in the fuel line could put out the flame, and continue to flow oil into the pot. The least problem that results is that the contents of the oil storage tank will be emptied into the boat cabin.
3. A pump is pressure operated, i.e., if oil in tank runs out, pump "runs wild" trying to bring up the pressure, thus burning itself out and possibly causing an electrical fire or at least completely discharging the vessel's battery.
4. Carburetor floats sometimes jam open when dirty or faulty, flooding the stove. The heat operated switch provides a back-up safety control.
It has been recognized that some safety defices for burners are desirable and a number of proposals have been made for safety devices for gas burners, gasoline burners and the like. For example, see U.S. Pat. Nos. 372,207, 2,381,591, 2,388,855 and 2,482,565. These patents, however, do not disclose devices suitable for use with an oil burning heater on a marine vessel.